Electrodes have been known which can be foraminous in structure. U.S. Pat. No. 4,370,214 describes an electrode prepared from filaments or fibers affixed to a support fabric. Metal is then deposited on the filaments, as by electroplating, which can result in a highly porous reticulate electrode. Such an electrode offers the advantage of a high surface area. In a related teaching in U.S. Pat. No. 4,350,580 there is disclosed a high surface area structure as a current distributor.
Battery electrodes may be made starting with a foam substrate material that is metallized. The polymer foam substrate of the metal foam can then be removed leaving a foam metal article. For example, U.S. Pat. No. 5,374,491 discusses an electrode produced from a raw material polymer foam in strip form which is electroplated. The thus obtained metallized foam may have the polymer substrate thermally decomposed and the metal annealed in a reducing atmosphere to obtain a reticulated metal sheet. The resulting reticulate article lends itself to high performance electrodes, especially as a high capacity, long life battery electrode.
The porous article with polymer substrate may not have the substrate removed, and may additionally contain other substituents. Such an article can find use as a flow-through electrode in removal of metal ions from a waste water stream, as described in U.S. Pat. No. 4,515,672. The reticulate cathode electrode is formed from an electroplated open cell polyurethane foam containing conductive carbon particles. The resulting reticulate article may be, for example, a copper plated cathode with the conductive carbon particles being retained in the final article.
Porous reticulates may also be formed using an open cell organic synthetic resinous material or an inorganic refractory material. For example, it is taught in U.S. Pat. No. 4,517,069 that a reticulate of titanium hydride may be produced by coating an open cell organic or inorganic substrate material, e.g., polystyrene beads serving as a "pore-former", with a slurry of titanium hydride particles and binder. The pore-former is removed, leaving the TiH.sub.2 reticulate. This reticulate can be sintered to yield a titanium metal reticulate. The reticulate may have a combination of large pores imparted by the substrate material in combination with micropores resulting from sintering effects. The reticulate has been taught to be effective as an electrode in an electrolytic chlor-alkali cell.
A reticulated electrical interface material may also be imposed between an electrode and a current distributor. Such a conductive interface material can be a compressible reticulated article, as taught in U.S. Pat. No. 4,657,650. The reticulate article provides for a multiplicity of contact points between the faces of the electrode and the current distributor, thereby enhancing electrical connection.
It has also been taught to use a fine screen foraminous material in conjunction with coarse screens as current distributors in electrolytic cells. Thus, U.S. Pat. No. 4,343,689 describes a coarse mesh cathode distributor screen having a finer mesh screen applied thereon. Such an arrangement provides a multiplicity of electrical contacts, such as to a particulate electrode that is bonded to a membrane.
It would, nevertheless, be desirable to provide an electrolytic cell with reduced cell resistivity, improving voltage savings. It would also be advantageous to enhance cell current efficiency. It would be advantageous to provide enhanced properties in a variety of processes, such as can be carried out in electrolytic cells, including chlorine and caustic production and salt splitting.